Small particles such as dust, smoke, organisms in the rooms of buildings, etc., generally tend to carry a positive electrical charge. Such small particles tend to be repelled bY the statically positive building structures and the like, and therefore to remain in suspension in the air.
It previously has been recognized that generation of negative ions will cause such positive particles of dust, smoke, etc., to be attracted to the ions, and to form sufficiently large particles physically that they will drop gravitationally to the earth or floor, as well as to be negatively charged for attraction to the earth, floor or walls. Negative ions also dispel static electricity which is often troublesome.
The foregoing has been recognized in the patent art, as for example U.S. Pat. Nos. 4,037,268 and 4,109,290, and the art of record therein, which discuss the benefits of removing particulate material from the air.
U.S. Pat. No. 4,672,504 discloses a generator for air purification, and specifically for the production of negative ions. This device is provided with a motor driven fan for circulating air. A housing is provided through which the air is circulated, and a large dome is housed within the housing. The dome is made of plastic or other insulating material and is hermetically sealed to a base within the housing.
The high voltage portions of this air purifier are disposed under the dome and hence in an inaccessible position, thereby assuring electrical safety. The inner surface of the dome is covered or coated with an electrically conductive material and a negative high voltage DC source is connected to the coating. This produces a negative electrostatic field over the entire outer surface of the dome. The outer surface of the dome then cause air particles to become negatively charged.